1. Field of the Invention
The invention relates to heating devices such as those used for cooking and baking foods and relates particularly to continuous cooking machines which comprise a rotatable circular surface which is heated interiorly by flames.
2. Description of Prior Art
Numerous heating or cooking devices are known in industry and particularly in the food industry which operate by virtue of contact wherein the surface of the heater is the outer surface of a revolving body which generally is metallic and which rotates around a substantially horizontal axis and on the interior of which is released heat energy produced by the combustion of a gas or a liquid or even a pulverized solid. Most often the revolving body is a cylinder, but it might likewise assume various other shapes and its outer surface, instead of being perfectly smooth, may have zones or areas provided with depressions or protrusions. For purposes of this application, the term "drum" and the like as used throughout the application should therefore not be narrowly construed to drums which are merely circular but extends instead of all equivalent structures whatever their general shape and whatever the state of their outer surfaces.
Generally, in the known materials up until now, the flames produced by burners which open adjacent to the interior wall of the heater each of which has a nozzle arranged in a direction substantially perpendicular to the corresponding diametral plane contact the interior surface before mixing between the flames in a turbulent or whirling movement occurs. The hot burned gases escape upwardly via the two ends of the drum thus creating a suction which draws the fresh air which penetrates via the ends of the drum so as to be brought towards the burners. As a result of this arrangement two inconveniences occur. The combustive fresh air mixes with the burned gas and is thus deprived of oxygen and, furthermore, the rush of fresh air cools the interior surface of the drum.
In certain apparatus, so as to avoid this cooling, the burners are fed with a mixture of air and of gas which is formed at the exterior of the drum. This solution to the problem requires a more complex installation, which is more costly and, furthermore, the transportation through the piping of the air-gas mixture raises serious dangers of explosion.